1. Main pump structure The main pump structure is shown in Figure 3-3.
2. Disassembly of the main pump of a modern excavator
①Choose a work place suitable for disassembly, lay a layer of rubber pad on the workbench to prevent parts from being injured.
② Remove the rust and dust on the pump surface with detergent.
③Remove the oil drain plug and drain the oil in the pump out of the pump casing (front pump and rear pump).
④Remove the hexagon bolt and remove the adjuster, as shown in Figure 3-4.
⑤ Remove the swash plate support, pump housing and valve block hexagon bolts, as shown in Figure 3-5. If a gear pump is installed behind the pump, remove the gear pump before removing the bolts.
⑥Place the pump flat on the workbench with the regulator facing down, and separate the pump casing from the valve block
⑦ Take the cylinder out of the pump casing, pull out the drive shaft directly, and at the same time pull out the plunger, setting plate, spherical bearing pad and cylinder spring, as shown in Figure 36.
During this process, be careful not to damage the sliding surfaces such as the cylinder block, spherical bearing pad, wrap foot and swash plate.
⑧ Remove the hexagon bolts, and then remove the front cover, as shown in Figure 3-7, screw the bolt into the pin hole on the front cover, so that the front cover is ejected, so that the cover can be easily removed. Because the oil seal is installed on the front cover, be careful not to damage the oil seal when removing the cover.
⑨ Remove the hexagon bolts, and then remove the rear cover. If installing a gear pump, first remove the gear pump.
⑩ Gently tap the flange part of the swash plate support on the side of the pump casing so that the swash plate support is separated from the pump casing, as shown in Figure 3-8.
① Remove the foot plate and swash plate from the pump casing, as shown in Figure 3-9.
② Lightly tap the shaft end of the drive shaft with a plastic hammer to remove it from the swash plate support, as shown in Figure 3-10 ① 3 Remove the valve plate from the valve block, as shown in Figure 3-11, this This work can be done in step ⑥.
④If necessary, the large stop block, small stop block, servo plunger and tilt pin must also be removed from the pump casing, and the needle bearing and spline connection must be removed from the valve block.
Note: When removing the tilt pin, use a clamp to prevent damage to the pin head: Be careful not to damage the servo plunger; try not to remove the needle bearing as much as possible, unless you replace the new needle bearing: do not loosen the valve block and the rotary oblique If the hex nut supported by the disc is loosened, the flow setting will change.
3. Main pump installation
①Reinstall in the reverse order of disassembly, pay attention to the following:
A. Repair damaged parts and prepare parts for replacement
B. Clean all parts with detergent and blow dry with compressed air.
C. Before installation, smear sliding parts, bearings, etc. with clean hydraulic oil.
Replace shape ring, oil seal and other seals
E. Use a torque wrench to tighten the bolts and plugs with the specified torque.
F. Be careful not to interchange the parts of the front and rear pumps
② Install the swash plate to the pump casing, and gently tap the swash plate support with a plastic hammer, as shown in Figure 3-12.
After removing the servo plunger, tilt pin, large stop block, and small stop block, install them on the pump casing as soon as possible for easy reassembly.
When tightening the servo plunger, use a clamp to prevent damage to the tilt pin head and feedback pin.
Apply Loctite (medium strength) to the threaded portion of the plunger.
③Turn the pump casing with the regulator face down, install the tilt bearing of the swash plate to the tilt pin, and install the swash plate to the swash plate support, as shown in Figure 3-13.
Use your fingers to move the swash plate and make sure that it can slide smoothly. Apply grease to the sliding surface and the swash plate support to facilitate the installation of the drive shaft.
④ Install the drive shaft with bearing, bearing spacer and snap ring to the swash plate support, as shown in Figure 3-14.
Do not hit the drive shaft with a hammer. After installation, gently tap the outer ring of the bearing with a plastic hammer to install each part into the support, install them in place with a brass punch ⑤ Install the front cover to the pump casing, and then install the hexagon bolts, as shown in Figure 3 -15 is shown.
Lightly grease the oil seal of the front cover. Be careful not to damage the oil seal when installing the oil seal. If it is a double pump, the method of installing the back cover and capping is similar.
⑥ Install the plunger cylinder assembly: cylinder body, plunger assembly, setting plate, spherical bearing, spacer and cylinder spring, then, the cylinder body and the plunger are inserted into the pump casing. Align the spline of the spherical bearing pad and the cylinder, and then align the spline of the drive shaft, as shown in Figure 3-16.
⑦ Install the valve plate on the valve block, insert the pin into the pin hole, as shown in Figure 3-17.
Note: Do not confuse the oil suction port and the oil outlet on the valve plate
⑧ Install the valve block on the pump casing and tighten the hexagon bolts, as shown in Figure 3-18.
Install the valve block on the rear pump first, so the installation is easier. Be careful not to confuse directions. Turn clockwise (viewed from the input shaft end), install the valve block with the regulator facing upwards, and the flange to the left (viewed from the front end). Turn counterclockwise (viewed from the end of the input shaft) with the flange to the right (viewed from the front end).
⑨ Install the feedback pin of the tilt pin on the regulator feedback pad, install the regulator, and tighten the hexagon bolts, taking care not to confuse the regulators of the front and rear pumps, as shown in Figure 3-19
⑩0 Install the drain plug
At this point, the reinstallation work is over.
